Alan Gertler - Academia.edu (original) (raw)
Papers by Alan Gertler
SAE Technical Paper Series, Nov 2, 2009
The Engineering Meetings Board has approved this paper for publication. It has successfully compl... more The Engineering Meetings Board has approved this paper for publication. It has successfully completed SAE's peer review process under the supervision of the session organizer. This process requires a minimum of three (3) reviews by industry experts. All rights reserved. No part of the publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE.
AGUSM, May 1, 2002
ABSTRACT Urban areas emit significant amounts of pollutants that impact forest ecosystems. One of... more ABSTRACT Urban areas emit significant amounts of pollutants that impact forest ecosystems. One of the most important of these is nitric acid vapor (HNO3), a nitrogen-containing gas that deposits efficiently to forest canopies. Since measuring HNO3 fluxes directly is often impractical and costly in remote forest locales, inferential techniques are most often used to estimate HNO3 flux. Given the highly efficient deposition of HNO3, many of these inferential models assume that leaf surfaces are a `perfect sink' for HNO3 (i.e., that resistance to HNO3 deposition is zero). This study tests the `perfect sink' assumption in an open gas exchange system by exposing Abies magnifica, Abies concolor, and Pinus jeffreyi seedlings to 1-13 ppb HNO3. We find that these cuticles are not perfect sinks for HNO3, with cuticular resistance values ranging from 20 to 184 s m-1 at these HNO3 concentrations. In addition, our results indicate that accumulating HNO3 on leaf cuticles at these concentrations leads to higher cuticular resistance over 8-12 hour exposure periods. Based on this laboratory data, we then parameterized cuticular resistance in a single layer inferential model for conditions in Lake Tahoe Basin forest canopies. Using this modification, modeled fluxes to the forest canopies were 33% lower during well-mixed daytime conditions than the fluxes from an identical model run using the infinite sink assumption. Thus, models that assume leaf cuticles to be a perfect HNO3 sink can substantially overestimate HNO3 flux. Since HNO3 can often account for more than half of atmospheric deposition, we conclude that inferential models that assume foliage to be perfect HNO3 sinks are inaccurate, especially in forests where significant amounts of HNO3 accumulate on leaf cuticles.
Springer eBooks, 2004
Lake Tahoe, which is located between the California-Nevada borders, is famous for its clarity; ho... more Lake Tahoe, which is located between the California-Nevada borders, is famous for its clarity; however, decline in Lake Tahoe’s water clarity was reported as 0.25 m per year1. Nutrient loading (phosphorus and nitrogen (N)) in last decades has been shown as the primary cause for this decline, and nearly half of total N input to the lake was attributed to atmospheric deposition.
Environmental Monitoring and Assessment, Nov 7, 2012
Air quality in Hyderabad, India, often exceeds the national ambient air quality standards, especi... more Air quality in Hyderabad, India, often exceeds the national ambient air quality standards, especially for particulate matter (PM), which, in 2010, averaged 82.2± 24.6, 96.2± 12.1, and 64.3 ± 21.2 μg/m 3 of PM 10 , at commercial, industrial, and residential monitoring stations, respectively, exceeding the national ambient standard of 60 μg/m 3. In 2005, following an ordinance passed by the Supreme Court of India, a source apportionment study was conducted to quantify source contributions to PM pollution in Hyderabad, using the chemical mass balance (version 8.2) receptor model for 180 ambient samples collected at three stations for PM 10 and PM 2.5 size fractions for three seasons. The receptor modeling results indicated that the PM 10 pollution is dominated by the direct vehicular exhaust and road dust (more than 60 %). PM 2.5 with higher propensity to enter the human respiratory tracks, has mixed sources of vehicle exhaust, industrial coal combustion, garbage burning, and secondary PM. In order to improve the air quality in the city, these findings demonstrate the need to control emissions from all known sources and particularly focus on the low-hanging fruits like road dust and waste burning, while the technological and institutional advancements in the transport and industrial sectors are bound to enhance efficiencies. Andhra Pradesh Pollution Control Board utilized these results to prepare an air pollution control action plan for the city.
Emissions from unpaved roadways were not targeted for sampling and analysis. This document descri... more Emissions from unpaved roadways were not targeted for sampling and analysis. This document describes the criteria used to select the field sampling sites, as well as the types of analyses that were performed at those sites. In addition, this document describes the results from the field work component of this study. Chemical mass balance analyses of highway particulate sources were conducted at two sites to determine the contributions of road sanding and salting operations to ambient levels at Albany, NY and at Reno, NV. Finally a set of experiments designed to assess diesel emissions were performed in the Ft. McHenry Tunnel (outside of Baltimore, MD) and in mid-town Manhattan. The Ft. McHenry Tunnel experiment produced emission factor estimates for heavy-duty diesel emission sources. Chemical mass balance analyses were performed in mid-town Manhattan to assess the contribution to ambient levels resulting from urban bus traffic. Results from the field work phase showed that paved road resuspension and road sanding and salting operations contribute significantly to the ambient levels, in the absence of other sources, contributing, in some cases, up to 60 percent of the total mass collected on the filters. In mid-town Manhattan, diesel emissions also contribute significantly to ambient levels;more » however, the emission factor results from the Ft. McHenry Tunnel indicated that emission from heavy-duty diesels were lower than published emission factors by approximate 50 percent.« less
Atmospheric Environment, Jun 1, 1996
Aktract-To obtain real-world motor vehicle emission rates for the hydrocarbon ozone precursors, a... more Aktract-To obtain real-world motor vehicle emission rates for the hydrocarbon ozone precursors, a series of experiments was conducted in the Fort McHenry Tunnel, Baltimore, Maryland and in the Tuscarora Mountain Tunnel, Pennsylvania. Air samples collected in the tunnels were analyzed for approximately 200 non-methane hydrocarbon (NMHC) species up to C2o, and formaldehyde. Emission rates were determined from tunnel inlet and outlet fluxes. Traffic composition analysis allowed emissions to be split into light-duty (LD; mostly spark-ignition) and heavy-duty (HD; mostly diesel) contributions. LD emissions of NMHC at Tuscarora were 293 mg/veh-mile, with paraffins constituting 35%, olefins 23%, aromatics 42%, and 6 mg/veh-mile of formaldehyde. At Fort McHenry, LD hydrocarbon emissions were 615 mg/veh-mile, with 38% paraffins, 18% olefms, and 44% aromatics, and 7 mg/veh-mile of formaldehyde. In both tunnels, HD emissions were approximately double LD emissions, but with higher percent paraffins, lower percent olefins, and an order of magnitude more formaldehyde. Through use of reactivity adjustment factors, the reactivity of the NMHC emissions with respect to ozone formation was assessed. Reactivity followed emissions, with HD emissions approximately twice the reactivity of LD emissions (on a per vehicle-mile basis). The mass specific reactivity (g-Oa/g-emission) was nearly constant among all vehicles. The effect of grade (assessed at Fort McHenry) was approximately a factor of 2 for both emissions and reactivity. However, since fuel-specific emissions (g-emission/gallon fuel consumed) for LD and HD vehicles were nearly independent of grade at Fort McHenry, the fuel-specific ozone reactivity (g-Oa/gallon fuel consumed) was also nearly constant over the down-and upgrades .
Science of The Total Environment, 2014
Bottom-up approach provides more geographic accurate traffic pollutant emission. • Geocoded spati... more Bottom-up approach provides more geographic accurate traffic pollutant emission. • Geocoded spatial and temporal road dust PM 10 emission factor in a road network • Integrated with TDM traffic activities into a regional emission inventory database • GIS tools to analyze each road link position to the lake • Combined dispersion modeling to estimate annual PM 10 deposition to Lake Tahoe
Atmospheric Environment, Nov 1, 2005
Ten air-quality samplings flights were performed over the San Diego metropolitan area during July... more Ten air-quality samplings flights were performed over the San Diego metropolitan area during July 2003. One of the objectives of these flights was to assess the contribution of the offshore pollution sources (civilian and military vessels) to the air quality in the region. The flights, which took place during the midday hours in the lower levels of the boundary layer, originated offshore and proceeded eastwards through a series of concentric arcs covering an area of approximately 600 km 2. The data from the continuous gas analyzers were translated to image plots that enabled the determination of the impact of the various sources on air quality. The results revealed that the offshore sources could often be detected (at least during five of the 10 flights) from their SO 2 plume. However, the area covered by these plumes and the concentrations were significantly lower than those measured over other parts of the domain due to sources south of the region. It was further observed that vehicular traffic contributed in a major source way to the formation of ozone. During most flights the pollution cloud, originating over the high traffic area in the vicinity of the downtown area, could be tracked 'downwind' until the completion of the photochemical processing. By then, most of the NO X had been converted to NO Z , and peak O 3 levels caused by the local emissions had started to ebb. Also, during most flights boundary layer peak levels of O 3 exceeded 100 ppbv, and in one case were above 140 ppbv.
Journal of the Air & Waste Management Association, Nov 1, 1999
In mid-1996, California implemented Phase 2 Reformulated Gasoline (RFG). The new fuel was designe... more In mid-1996, California implemented Phase 2 Reformulated Gasoline (RFG). The new fuel was designed to further decrease emissions of hydrocarbons (HCs), oxides of nitrogen (NO x), carbon monoxide (CO), sulfur dioxide (SO 2), and other toxic species. In addition, it was formulated to reduce the ozone-forming potential of the HCs emitted by vehicles. Previous studies have observed that emissions from on-road vehicles can differ significantly from those predicted by mobile source emissions models, and so it is important to quantify the change in emissions in a real-world setting. In October 1995, prior to the introduction of California Phase 2 RFG, the Desert Research Institute (DRI) performed a study of vehicle emissions in Los Angeles' Sepulveda Tunnel. This study provided a baseline against which the results of a second experiment, conducted in July 1996, could be compared to evaluate the impact of California Phase 2 RFG on emissions from real-world vehicles. Compared with the 1995 experiment, CO and NO x emissions exhibited statistically significant decreases, while the decrease in non-methane hydrocarbon emissions was not statistically significant. Changes in the speciated HC emissions were evaluated. The benzene emission rate decreased by 27% and the overall emission rate of aromatic compounds decreased by 22% comparing the runs with similar speeds. Emissions of alkenes were virtually unchanged; however, emissions of combustion related unsaturates (e.g., acetylene, ethene) increased, while heavier alkenes decreased. The emission rate of methyl tertiary butyl ether (MTBE) exhibited a larger increase. Overall changes in the ozone-forming potential IMPLICATIONS In an effort to reduce tailpipe emissions from light-duty vehicles, California introduced Phase 2 RFG in the spring of 1996. In contrast to what was expected, the observed on-road emissions of HCs and the reactivity of the emissions did not significantly change following the implementation of the new fuel. Observed CO, NO x , and aromatic HC emissions were reduced. of the emissions were not significantly different, with the increased contributions to reactivity from paraffins, olefins, and MTBE being offset by a large decrease in reactivity due to aromatics.
Atmospheric Environment, Dec 1, 2003
Intensive measurements were performed at roadside locations in Reno, Nevada, and Durham/Research ... more Intensive measurements were performed at roadside locations in Reno, Nevada, and Durham/Research Triangle Park, North Carolina to derive mass emission factors from on-road vehicles. Measurements included continuous particulate matter (PM) concentrations (PM 2.5 , and PM 10), wind speed, wind direction, and vehicle number, class, and speed. A multi-lag linear regression approach was applied to calculate mass emission rates using the continuous data. The output of the multi-lag regression model, the regression coefficients, along with the vehicle specifications and the wind speed/direction at each site were then used to calculate mass emission factors for light-duty spark ignition (LDSI) and heavy-duty diesel (HDD) vehicles.
Atmospheric Environment, Feb 1, 2009
The structure and design of future urban development can have significant adverse effects on air ... more The structure and design of future urban development can have significant adverse effects on air pollutant emissions as well as other environmental factors. When considering the future impact of growth on mobile source emissions, we generally model the increase in vehicle kilometers traveled (VKT) as a function of population growth. However, diverse and poorly planned urban development (i.e., urban sprawl)
Atmospheric Environment, Apr 1, 2005
In the US, the majority of the on-road fleet and vehicle miles travelled are attributed to light-... more In the US, the majority of the on-road fleet and vehicle miles travelled are attributed to light-duty vehicles, which are fuelled almost entirely by gasoline. However, due to their significantly higher PM emission rates, emissions inventories have tended to attribute the majority of the mobile source PM to contributions from heavy-duty diesel vehicles and strategies to reduce mobile source PM have focused on the contribution from this source. A limited number of source attribution studies have implied that PM emission inventories overestimate the diesel contribution and emissions from gasoline vehicles may be greater than previously believed. Other receptor-modelling studies have found diesel vehicles to be the dominant source of motor vehicle PM. The former conclusion is supported by recent on-road PM emission rate results obtained in a highway tunnel and a series of crossroad experiments. This paper describes the often-conflicting results obtained from receptor modelling studies and emission inventories and uses on-road emission factor results to estimate the relative contributions from the diesel and gasoline sectors of the fleet.
Atmospheric Environment, Oct 1, 2006
Resuspended road dust is an important contributor to ambient particulate matter (PM). In areas wi... more Resuspended road dust is an important contributor to ambient particulate matter (PM). In areas with significant snow events, the use of wintertime roadway abrasives for traction control can result in increased PM emissions. An alternative control measure is to use chemical deicers prior to a snow event to minimize ice formation and reduce the need for abrasives. Street sweeping is also commonly used to reduce the impact of re-entrained abrasive material after the snow pack on the road has cleared. In this study, we performed roadside measurements of PM flux and instrumented vehicle PM measurements to evaluate the effectiveness of street sweeping to reduce dust re-entrainment and assess the impact of abrasives and deicers on ambient PM near an alpine lake (Lake Tahoe). The results indicate use of liquid deicers contributes less to road dust emissions than abrasives. Street sweeping was found to increase the PM 10 re-entrainment rate of the remaining road dust. Emission factors for roads in the study area (a snowy mountain climate) tend to decrease significantly from late Spring to early Summer by as much as a factor of 4.
Atmospheric Environment, Jun 1, 1996
Samples were collected using stainless steel canisters (whole air samples, analyzed for C2-C12 hy... more Samples were collected using stainless steel canisters (whole air samples, analyzed for C2-C12 hydrocarbons), Tenax-TA solid adsorbent cartridges (for semi-volatile hydrocarbons, in the Cs-C20 range), and 2,4-dinitrophenylhydrazine (DNPH) impregnated cartridges (for carbonyl compounds). The samples were analyzed using high resolution gas chromatographic separation with Fourier transform infrared/mass spectrometric detection (GC/IRD/ MSD) for qualitative identification and with flame ionization detection (GC/FID) for quantitation of hydrocarbons, and high performance liquid chromatography (HPLC) for identification and quantitation of carbonyl compounds. A custom-designed database management system was used to handle the large data sets generated by these analyses. From the evaluation of canister and Tenax sample stability upon storage, it was found that hydrocarbons in the Cs-C12 range seemed to be more stable in the Tenax cartridge than in the canister. The effect of the Nation ® dryer (frequently used for moisture removal prior to cryogenic concentration of the canister samples) was also assessed and it was found to lower the measured concentrations of hydrocarbons collected in the canisters. Comparison of hydrocarbon concentrations found in the Tenax and canister samples allows an assessment of the contribution of semi-v01atile hydrocarbons (C1o-C2o range derived from Tenax data) to the total non-methane hydrocarbons (C2-C2o, derived from canisters and Tenax data). The results of this study show that hydrocarbons in the range of C~o-C2o are important components of gas-phase hydrocarbons emitted from heavy-duty diesel vehicles (they account for approximately half of the total gas-phase non-methane hydrocarbon emission rates) and hence that solid adsorbent sampling should be used in addition to canister sampling in measurements of motor vehicle emissions.
Atmospheric Environment, Jun 1, 1996
Al~ract-Motor vehicle emission rates of CO, NO, NOx, and gas-phase speciated nonmethane hydrocarb... more Al~ract-Motor vehicle emission rates of CO, NO, NOx, and gas-phase speciated nonmethane hydrocarbons (NMHC) and carbonyl compounds were measured in 1992 in the Fort McHenry Tunnel under Baltimore Harbor and in the Tuscarora Mountain Tunnel of the Pennsylvania Turnpike, for comparison with emission-model predictions and for calculation of the reactivity of vehicle emissions with respect to 03 formation. Both tunnels represent a high-speed setting at relatively steady speed. The cars at both sites tended to be newer than elsewhere (median age was < 4 yr), and much better maintained as judged by low CO/CO2 ratios and other emissions characteristics. The Tuscarora Mountain Tunnel is flat, making it advantageous for testing automotive emission models, while in the underwater Fort McHenry Tunnel the impact of roadway grade can be evaluated. MOBILE4.1 and MOBILE5 gave predictions within + 50% of observation most of the time. Tbere was a tendency to overpredict, especially with MOBILE5 and especially at Tuscarora. However, fight-dutyvehicle CO, NMHC, and NOx all were underpredicted by MOBILE4.1 at Fort McHenry. Light-dutyvehicle CO/NO~ ratios and NMHC/NO~ ratios were generally a little higher than predicted. The comparability of the predictions to the observations contrasts with a 1987 experiment in an urban tunnel (Van Nuys) where CO and HC, as well as CO/NO~ and NMHC/NO~ ratios, were grossly underpredicted. The effect of roadway grade on gram per mile (g mi-1) emissions was substantial. Fuel-specific emissions (g gal-1), however, were almost independent of roadway grade, which suggests a potential virtue in emissions models based on fuel-specific emissions rather than g mi-1 emissions. Some 200 NMHC and carbonyl emissions species were quantified as to their light-and heavy-dutyvehicle emission rates. The heavy-duty-vehicle NMHC emissions were calculated to possess more reactivity, per vehicle-mile, with respect to 03 formation (g 03 per vehicle-mile) than did the light-duty-vehicle NMHC emissions. Per gallon of fuel consumed, the light-duty vehicles had the greater reactivity. Much of the NMHC, and much of their reactivity with respect to O3 formation, resided in compounds heavier than Cto, mostly from beavy-duty diesels, implying that atmospheric NMHC sampling with canisters alone is inadequate in at least some situations since canisters were found not to be quantitative beyond ~ C1o. The contrasting lack of compounds heavier than C1o from light-duty vehicles suggests a way to separate light-and heavy-duty-vehicle contributions in receptor modeling source apportionment. The division between light-duty-vehicle tailpipe and nontaiipipe NMHC emissions was ~ 85% tailpipe and ~ 15% nontailpipe (evaporative running losses, etc.). Measured CO/CO2 ratios agreed well with concurrent roadside infrared remote sensing measurements on light-duty vehicles, although remote sensing HC/CO2 ratio measurements were not successful at the low HC levels prevailing. Remote sensing measurements on heavy-duty diesels were obtained for the first time, and were roughly in agreement with the regular (bag sampling) tunnel measurements in both CO/CO2 and HC/CO2 ratios. A number of recommendations for further experiments, measurement methodology development, and emissions model development and evaluation are offered.
AGUFM, Dec 1, 2008
Starting in the second half of the 20th century, decline in Lake Tahoe's water clarity and d... more Starting in the second half of the 20th century, decline in Lake Tahoe's water clarity and degradation in the basin's air quality have become major concerns due to its unique scenic features. Gaseous and particulate nitrogen (N) and particulate phosphorus (P) loading via direct atmospheric deposition and sediment transport to the lake have also been implicated as responsible for its eutrophication and decline in water clarity. Estimates suggest that atmospheric N deposition contributes 55% of the total N loading to the lake, while atmospheric P deposition contributes 15% of the total P loading. In order to improve both air quality and, as a consequence, water quality, it is necessary to develop an understanding of the sources of the atmospheric pollutants. Once this is accomplished, it is possible to implement cost-effective strategies to reduce this impact. This paper summarizes the findings of a series of studies performed to determine the levels and sources of ambient air pollutants in the basin. Projects have included the development of a Tahoe-specific emissions inventory, long-term measurements of road dust resuspension, modeling to determine the fraction of pollutants coming from in-basin vs. out-of-basin sources, particulate source apportionment, and estimates of nitric acid deposition. These studies found that the pollutants most closely connected to the decline in water quality come largely from within basin sources, as opposed to those coming from the Central Valley and upwind urban areas of California. These results indicate regulators need to control pollutant emissions within the Tahoe basin in order to reduce the impact of atmospheric pollutants on both air and water quality.
CRC Press eBooks, Jan 14, 2009
SAE Technical Paper Series, Nov 2, 2009
The Engineering Meetings Board has approved this paper for publication. It has successfully compl... more The Engineering Meetings Board has approved this paper for publication. It has successfully completed SAE's peer review process under the supervision of the session organizer. This process requires a minimum of three (3) reviews by industry experts. All rights reserved. No part of the publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE.
AGUSM, May 1, 2002
ABSTRACT Urban areas emit significant amounts of pollutants that impact forest ecosystems. One of... more ABSTRACT Urban areas emit significant amounts of pollutants that impact forest ecosystems. One of the most important of these is nitric acid vapor (HNO3), a nitrogen-containing gas that deposits efficiently to forest canopies. Since measuring HNO3 fluxes directly is often impractical and costly in remote forest locales, inferential techniques are most often used to estimate HNO3 flux. Given the highly efficient deposition of HNO3, many of these inferential models assume that leaf surfaces are a `perfect sink' for HNO3 (i.e., that resistance to HNO3 deposition is zero). This study tests the `perfect sink' assumption in an open gas exchange system by exposing Abies magnifica, Abies concolor, and Pinus jeffreyi seedlings to 1-13 ppb HNO3. We find that these cuticles are not perfect sinks for HNO3, with cuticular resistance values ranging from 20 to 184 s m-1 at these HNO3 concentrations. In addition, our results indicate that accumulating HNO3 on leaf cuticles at these concentrations leads to higher cuticular resistance over 8-12 hour exposure periods. Based on this laboratory data, we then parameterized cuticular resistance in a single layer inferential model for conditions in Lake Tahoe Basin forest canopies. Using this modification, modeled fluxes to the forest canopies were 33% lower during well-mixed daytime conditions than the fluxes from an identical model run using the infinite sink assumption. Thus, models that assume leaf cuticles to be a perfect HNO3 sink can substantially overestimate HNO3 flux. Since HNO3 can often account for more than half of atmospheric deposition, we conclude that inferential models that assume foliage to be perfect HNO3 sinks are inaccurate, especially in forests where significant amounts of HNO3 accumulate on leaf cuticles.
Springer eBooks, 2004
Lake Tahoe, which is located between the California-Nevada borders, is famous for its clarity; ho... more Lake Tahoe, which is located between the California-Nevada borders, is famous for its clarity; however, decline in Lake Tahoe’s water clarity was reported as 0.25 m per year1. Nutrient loading (phosphorus and nitrogen (N)) in last decades has been shown as the primary cause for this decline, and nearly half of total N input to the lake was attributed to atmospheric deposition.
Environmental Monitoring and Assessment, Nov 7, 2012
Air quality in Hyderabad, India, often exceeds the national ambient air quality standards, especi... more Air quality in Hyderabad, India, often exceeds the national ambient air quality standards, especially for particulate matter (PM), which, in 2010, averaged 82.2± 24.6, 96.2± 12.1, and 64.3 ± 21.2 μg/m 3 of PM 10 , at commercial, industrial, and residential monitoring stations, respectively, exceeding the national ambient standard of 60 μg/m 3. In 2005, following an ordinance passed by the Supreme Court of India, a source apportionment study was conducted to quantify source contributions to PM pollution in Hyderabad, using the chemical mass balance (version 8.2) receptor model for 180 ambient samples collected at three stations for PM 10 and PM 2.5 size fractions for three seasons. The receptor modeling results indicated that the PM 10 pollution is dominated by the direct vehicular exhaust and road dust (more than 60 %). PM 2.5 with higher propensity to enter the human respiratory tracks, has mixed sources of vehicle exhaust, industrial coal combustion, garbage burning, and secondary PM. In order to improve the air quality in the city, these findings demonstrate the need to control emissions from all known sources and particularly focus on the low-hanging fruits like road dust and waste burning, while the technological and institutional advancements in the transport and industrial sectors are bound to enhance efficiencies. Andhra Pradesh Pollution Control Board utilized these results to prepare an air pollution control action plan for the city.
Emissions from unpaved roadways were not targeted for sampling and analysis. This document descri... more Emissions from unpaved roadways were not targeted for sampling and analysis. This document describes the criteria used to select the field sampling sites, as well as the types of analyses that were performed at those sites. In addition, this document describes the results from the field work component of this study. Chemical mass balance analyses of highway particulate sources were conducted at two sites to determine the contributions of road sanding and salting operations to ambient levels at Albany, NY and at Reno, NV. Finally a set of experiments designed to assess diesel emissions were performed in the Ft. McHenry Tunnel (outside of Baltimore, MD) and in mid-town Manhattan. The Ft. McHenry Tunnel experiment produced emission factor estimates for heavy-duty diesel emission sources. Chemical mass balance analyses were performed in mid-town Manhattan to assess the contribution to ambient levels resulting from urban bus traffic. Results from the field work phase showed that paved road resuspension and road sanding and salting operations contribute significantly to the ambient levels, in the absence of other sources, contributing, in some cases, up to 60 percent of the total mass collected on the filters. In mid-town Manhattan, diesel emissions also contribute significantly to ambient levels;more » however, the emission factor results from the Ft. McHenry Tunnel indicated that emission from heavy-duty diesels were lower than published emission factors by approximate 50 percent.« less
Atmospheric Environment, Jun 1, 1996
Aktract-To obtain real-world motor vehicle emission rates for the hydrocarbon ozone precursors, a... more Aktract-To obtain real-world motor vehicle emission rates for the hydrocarbon ozone precursors, a series of experiments was conducted in the Fort McHenry Tunnel, Baltimore, Maryland and in the Tuscarora Mountain Tunnel, Pennsylvania. Air samples collected in the tunnels were analyzed for approximately 200 non-methane hydrocarbon (NMHC) species up to C2o, and formaldehyde. Emission rates were determined from tunnel inlet and outlet fluxes. Traffic composition analysis allowed emissions to be split into light-duty (LD; mostly spark-ignition) and heavy-duty (HD; mostly diesel) contributions. LD emissions of NMHC at Tuscarora were 293 mg/veh-mile, with paraffins constituting 35%, olefins 23%, aromatics 42%, and 6 mg/veh-mile of formaldehyde. At Fort McHenry, LD hydrocarbon emissions were 615 mg/veh-mile, with 38% paraffins, 18% olefms, and 44% aromatics, and 7 mg/veh-mile of formaldehyde. In both tunnels, HD emissions were approximately double LD emissions, but with higher percent paraffins, lower percent olefins, and an order of magnitude more formaldehyde. Through use of reactivity adjustment factors, the reactivity of the NMHC emissions with respect to ozone formation was assessed. Reactivity followed emissions, with HD emissions approximately twice the reactivity of LD emissions (on a per vehicle-mile basis). The mass specific reactivity (g-Oa/g-emission) was nearly constant among all vehicles. The effect of grade (assessed at Fort McHenry) was approximately a factor of 2 for both emissions and reactivity. However, since fuel-specific emissions (g-emission/gallon fuel consumed) for LD and HD vehicles were nearly independent of grade at Fort McHenry, the fuel-specific ozone reactivity (g-Oa/gallon fuel consumed) was also nearly constant over the down-and upgrades .
Science of The Total Environment, 2014
Bottom-up approach provides more geographic accurate traffic pollutant emission. • Geocoded spati... more Bottom-up approach provides more geographic accurate traffic pollutant emission. • Geocoded spatial and temporal road dust PM 10 emission factor in a road network • Integrated with TDM traffic activities into a regional emission inventory database • GIS tools to analyze each road link position to the lake • Combined dispersion modeling to estimate annual PM 10 deposition to Lake Tahoe
Atmospheric Environment, Nov 1, 2005
Ten air-quality samplings flights were performed over the San Diego metropolitan area during July... more Ten air-quality samplings flights were performed over the San Diego metropolitan area during July 2003. One of the objectives of these flights was to assess the contribution of the offshore pollution sources (civilian and military vessels) to the air quality in the region. The flights, which took place during the midday hours in the lower levels of the boundary layer, originated offshore and proceeded eastwards through a series of concentric arcs covering an area of approximately 600 km 2. The data from the continuous gas analyzers were translated to image plots that enabled the determination of the impact of the various sources on air quality. The results revealed that the offshore sources could often be detected (at least during five of the 10 flights) from their SO 2 plume. However, the area covered by these plumes and the concentrations were significantly lower than those measured over other parts of the domain due to sources south of the region. It was further observed that vehicular traffic contributed in a major source way to the formation of ozone. During most flights the pollution cloud, originating over the high traffic area in the vicinity of the downtown area, could be tracked 'downwind' until the completion of the photochemical processing. By then, most of the NO X had been converted to NO Z , and peak O 3 levels caused by the local emissions had started to ebb. Also, during most flights boundary layer peak levels of O 3 exceeded 100 ppbv, and in one case were above 140 ppbv.
Journal of the Air & Waste Management Association, Nov 1, 1999
In mid-1996, California implemented Phase 2 Reformulated Gasoline (RFG). The new fuel was designe... more In mid-1996, California implemented Phase 2 Reformulated Gasoline (RFG). The new fuel was designed to further decrease emissions of hydrocarbons (HCs), oxides of nitrogen (NO x), carbon monoxide (CO), sulfur dioxide (SO 2), and other toxic species. In addition, it was formulated to reduce the ozone-forming potential of the HCs emitted by vehicles. Previous studies have observed that emissions from on-road vehicles can differ significantly from those predicted by mobile source emissions models, and so it is important to quantify the change in emissions in a real-world setting. In October 1995, prior to the introduction of California Phase 2 RFG, the Desert Research Institute (DRI) performed a study of vehicle emissions in Los Angeles' Sepulveda Tunnel. This study provided a baseline against which the results of a second experiment, conducted in July 1996, could be compared to evaluate the impact of California Phase 2 RFG on emissions from real-world vehicles. Compared with the 1995 experiment, CO and NO x emissions exhibited statistically significant decreases, while the decrease in non-methane hydrocarbon emissions was not statistically significant. Changes in the speciated HC emissions were evaluated. The benzene emission rate decreased by 27% and the overall emission rate of aromatic compounds decreased by 22% comparing the runs with similar speeds. Emissions of alkenes were virtually unchanged; however, emissions of combustion related unsaturates (e.g., acetylene, ethene) increased, while heavier alkenes decreased. The emission rate of methyl tertiary butyl ether (MTBE) exhibited a larger increase. Overall changes in the ozone-forming potential IMPLICATIONS In an effort to reduce tailpipe emissions from light-duty vehicles, California introduced Phase 2 RFG in the spring of 1996. In contrast to what was expected, the observed on-road emissions of HCs and the reactivity of the emissions did not significantly change following the implementation of the new fuel. Observed CO, NO x , and aromatic HC emissions were reduced. of the emissions were not significantly different, with the increased contributions to reactivity from paraffins, olefins, and MTBE being offset by a large decrease in reactivity due to aromatics.
Atmospheric Environment, Dec 1, 2003
Intensive measurements were performed at roadside locations in Reno, Nevada, and Durham/Research ... more Intensive measurements were performed at roadside locations in Reno, Nevada, and Durham/Research Triangle Park, North Carolina to derive mass emission factors from on-road vehicles. Measurements included continuous particulate matter (PM) concentrations (PM 2.5 , and PM 10), wind speed, wind direction, and vehicle number, class, and speed. A multi-lag linear regression approach was applied to calculate mass emission rates using the continuous data. The output of the multi-lag regression model, the regression coefficients, along with the vehicle specifications and the wind speed/direction at each site were then used to calculate mass emission factors for light-duty spark ignition (LDSI) and heavy-duty diesel (HDD) vehicles.
Atmospheric Environment, Feb 1, 2009
The structure and design of future urban development can have significant adverse effects on air ... more The structure and design of future urban development can have significant adverse effects on air pollutant emissions as well as other environmental factors. When considering the future impact of growth on mobile source emissions, we generally model the increase in vehicle kilometers traveled (VKT) as a function of population growth. However, diverse and poorly planned urban development (i.e., urban sprawl)
Atmospheric Environment, Apr 1, 2005
In the US, the majority of the on-road fleet and vehicle miles travelled are attributed to light-... more In the US, the majority of the on-road fleet and vehicle miles travelled are attributed to light-duty vehicles, which are fuelled almost entirely by gasoline. However, due to their significantly higher PM emission rates, emissions inventories have tended to attribute the majority of the mobile source PM to contributions from heavy-duty diesel vehicles and strategies to reduce mobile source PM have focused on the contribution from this source. A limited number of source attribution studies have implied that PM emission inventories overestimate the diesel contribution and emissions from gasoline vehicles may be greater than previously believed. Other receptor-modelling studies have found diesel vehicles to be the dominant source of motor vehicle PM. The former conclusion is supported by recent on-road PM emission rate results obtained in a highway tunnel and a series of crossroad experiments. This paper describes the often-conflicting results obtained from receptor modelling studies and emission inventories and uses on-road emission factor results to estimate the relative contributions from the diesel and gasoline sectors of the fleet.
Atmospheric Environment, Oct 1, 2006
Resuspended road dust is an important contributor to ambient particulate matter (PM). In areas wi... more Resuspended road dust is an important contributor to ambient particulate matter (PM). In areas with significant snow events, the use of wintertime roadway abrasives for traction control can result in increased PM emissions. An alternative control measure is to use chemical deicers prior to a snow event to minimize ice formation and reduce the need for abrasives. Street sweeping is also commonly used to reduce the impact of re-entrained abrasive material after the snow pack on the road has cleared. In this study, we performed roadside measurements of PM flux and instrumented vehicle PM measurements to evaluate the effectiveness of street sweeping to reduce dust re-entrainment and assess the impact of abrasives and deicers on ambient PM near an alpine lake (Lake Tahoe). The results indicate use of liquid deicers contributes less to road dust emissions than abrasives. Street sweeping was found to increase the PM 10 re-entrainment rate of the remaining road dust. Emission factors for roads in the study area (a snowy mountain climate) tend to decrease significantly from late Spring to early Summer by as much as a factor of 4.
Atmospheric Environment, Jun 1, 1996
Samples were collected using stainless steel canisters (whole air samples, analyzed for C2-C12 hy... more Samples were collected using stainless steel canisters (whole air samples, analyzed for C2-C12 hydrocarbons), Tenax-TA solid adsorbent cartridges (for semi-volatile hydrocarbons, in the Cs-C20 range), and 2,4-dinitrophenylhydrazine (DNPH) impregnated cartridges (for carbonyl compounds). The samples were analyzed using high resolution gas chromatographic separation with Fourier transform infrared/mass spectrometric detection (GC/IRD/ MSD) for qualitative identification and with flame ionization detection (GC/FID) for quantitation of hydrocarbons, and high performance liquid chromatography (HPLC) for identification and quantitation of carbonyl compounds. A custom-designed database management system was used to handle the large data sets generated by these analyses. From the evaluation of canister and Tenax sample stability upon storage, it was found that hydrocarbons in the Cs-C12 range seemed to be more stable in the Tenax cartridge than in the canister. The effect of the Nation ® dryer (frequently used for moisture removal prior to cryogenic concentration of the canister samples) was also assessed and it was found to lower the measured concentrations of hydrocarbons collected in the canisters. Comparison of hydrocarbon concentrations found in the Tenax and canister samples allows an assessment of the contribution of semi-v01atile hydrocarbons (C1o-C2o range derived from Tenax data) to the total non-methane hydrocarbons (C2-C2o, derived from canisters and Tenax data). The results of this study show that hydrocarbons in the range of C~o-C2o are important components of gas-phase hydrocarbons emitted from heavy-duty diesel vehicles (they account for approximately half of the total gas-phase non-methane hydrocarbon emission rates) and hence that solid adsorbent sampling should be used in addition to canister sampling in measurements of motor vehicle emissions.
Atmospheric Environment, Jun 1, 1996
Al~ract-Motor vehicle emission rates of CO, NO, NOx, and gas-phase speciated nonmethane hydrocarb... more Al~ract-Motor vehicle emission rates of CO, NO, NOx, and gas-phase speciated nonmethane hydrocarbons (NMHC) and carbonyl compounds were measured in 1992 in the Fort McHenry Tunnel under Baltimore Harbor and in the Tuscarora Mountain Tunnel of the Pennsylvania Turnpike, for comparison with emission-model predictions and for calculation of the reactivity of vehicle emissions with respect to 03 formation. Both tunnels represent a high-speed setting at relatively steady speed. The cars at both sites tended to be newer than elsewhere (median age was < 4 yr), and much better maintained as judged by low CO/CO2 ratios and other emissions characteristics. The Tuscarora Mountain Tunnel is flat, making it advantageous for testing automotive emission models, while in the underwater Fort McHenry Tunnel the impact of roadway grade can be evaluated. MOBILE4.1 and MOBILE5 gave predictions within + 50% of observation most of the time. Tbere was a tendency to overpredict, especially with MOBILE5 and especially at Tuscarora. However, fight-dutyvehicle CO, NMHC, and NOx all were underpredicted by MOBILE4.1 at Fort McHenry. Light-dutyvehicle CO/NO~ ratios and NMHC/NO~ ratios were generally a little higher than predicted. The comparability of the predictions to the observations contrasts with a 1987 experiment in an urban tunnel (Van Nuys) where CO and HC, as well as CO/NO~ and NMHC/NO~ ratios, were grossly underpredicted. The effect of roadway grade on gram per mile (g mi-1) emissions was substantial. Fuel-specific emissions (g gal-1), however, were almost independent of roadway grade, which suggests a potential virtue in emissions models based on fuel-specific emissions rather than g mi-1 emissions. Some 200 NMHC and carbonyl emissions species were quantified as to their light-and heavy-dutyvehicle emission rates. The heavy-duty-vehicle NMHC emissions were calculated to possess more reactivity, per vehicle-mile, with respect to 03 formation (g 03 per vehicle-mile) than did the light-duty-vehicle NMHC emissions. Per gallon of fuel consumed, the light-duty vehicles had the greater reactivity. Much of the NMHC, and much of their reactivity with respect to O3 formation, resided in compounds heavier than Cto, mostly from beavy-duty diesels, implying that atmospheric NMHC sampling with canisters alone is inadequate in at least some situations since canisters were found not to be quantitative beyond ~ C1o. The contrasting lack of compounds heavier than C1o from light-duty vehicles suggests a way to separate light-and heavy-duty-vehicle contributions in receptor modeling source apportionment. The division between light-duty-vehicle tailpipe and nontaiipipe NMHC emissions was ~ 85% tailpipe and ~ 15% nontailpipe (evaporative running losses, etc.). Measured CO/CO2 ratios agreed well with concurrent roadside infrared remote sensing measurements on light-duty vehicles, although remote sensing HC/CO2 ratio measurements were not successful at the low HC levels prevailing. Remote sensing measurements on heavy-duty diesels were obtained for the first time, and were roughly in agreement with the regular (bag sampling) tunnel measurements in both CO/CO2 and HC/CO2 ratios. A number of recommendations for further experiments, measurement methodology development, and emissions model development and evaluation are offered.
AGUFM, Dec 1, 2008
Starting in the second half of the 20th century, decline in Lake Tahoe's water clarity and d... more Starting in the second half of the 20th century, decline in Lake Tahoe's water clarity and degradation in the basin's air quality have become major concerns due to its unique scenic features. Gaseous and particulate nitrogen (N) and particulate phosphorus (P) loading via direct atmospheric deposition and sediment transport to the lake have also been implicated as responsible for its eutrophication and decline in water clarity. Estimates suggest that atmospheric N deposition contributes 55% of the total N loading to the lake, while atmospheric P deposition contributes 15% of the total P loading. In order to improve both air quality and, as a consequence, water quality, it is necessary to develop an understanding of the sources of the atmospheric pollutants. Once this is accomplished, it is possible to implement cost-effective strategies to reduce this impact. This paper summarizes the findings of a series of studies performed to determine the levels and sources of ambient air pollutants in the basin. Projects have included the development of a Tahoe-specific emissions inventory, long-term measurements of road dust resuspension, modeling to determine the fraction of pollutants coming from in-basin vs. out-of-basin sources, particulate source apportionment, and estimates of nitric acid deposition. These studies found that the pollutants most closely connected to the decline in water quality come largely from within basin sources, as opposed to those coming from the Central Valley and upwind urban areas of California. These results indicate regulators need to control pollutant emissions within the Tahoe basin in order to reduce the impact of atmospheric pollutants on both air and water quality.
CRC Press eBooks, Jan 14, 2009